Increasingly, many portable consumer electronics devices, such as mobile phones, portable digital assistants (PDA) and portable audio players comprise embedded computer systems. These embedded computer systems are typically configured according to general-purpose computer hardware platforms or architecture templates. The only difference between these consumer electronic devices is typically the software application that is being executed on the particular device. Further, several different functionalities are increasingly being clubbed into one device. For example, some mobile phones also work as portable digital assistants (PDA) and/or portable audio players. Accordingly, there has been a shift of focus in the portable embedded computer systems domain towards appropriate software-implementations of different functionalities, rather than tailor-made hardware for different applications.
Power consumption of the computer systems embedded in the portable devices is probably the most critical constraint in the design of both, hardware and software, for such portable devices. One known method of minimising power consumption of computer systems embedded in portable devices is to dynamically scale the voltage and frequency (i.e., clock frequency) of the processor of an embedded computer system in response to the variable workload involved in processing multimedia streams.
Another known method of minimising power consumption of computer systems embedded in portable devices uses buffers to smooth out multimedia streams and decouple two architectural components having different processing rates. This enables the embedded processor to be periodically switched off or for the processor to be run at a lower frequency, thereby saving energy. There are also a number of known scheduling methods addressed at the problem of maintaining a Quality-of-Service (QoS) requirement associated with multimedia applications and at the same time minimizing power consumption of an embedded computer system.